The menu isn't on the page you link to, so that's no wonder. The menu you use is already based on CSS.

I don't see any drop in the version of IE I have installed, but it suggests that the width of the menu is too small to contain all links on one line, at least in that version of IE, maybe because of a bug or peculiarity in that version.

It seems to vary depending on the browser. FF on my laptop drops the last 2 items. Now, on my desktop, FF, Chrome, and Opera drop only the last item, and Safari doesn't drop any. Disabling the minimum font size doesn't change it either.